settings - How do I change the time zone (which is disabled) in Honeycomb on a Samsung Galaxy Tab 10.1?

When I first turned on my Galaxy Tab 10.1, I told it to automatically set the time. Unfortunately now the time zone is set to GMT+00:00 in the Date & time settings, and is disabled (so I can't change it). How do I enable the time zone setting so I can change it?

Answer

I downloaded a free app called TimeZone Changer to fix this problem. Still don't understand why Samsung disables this.